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Testing the Strong Equivalence Principle: Detection of the External Field Effect in Rotationally Supported Galaxies
- Publication Year :
- 2020
-
Abstract
- The strong equivalence principle (SEP) distinguishes General Relativity from other viable theories of gravity. The SEP demands that the internal dynamics of a self-gravitating system under free-fall in an external gravitational field should not depend on the external field strength. We test the SEP by investigating the external field effect (EFE) in Milgromian dynamics (MOND), proposed as an alternative to dark matter in interpreting galactic kinematics. We report a detection of this EFE using galaxies from the Spitzer Photometry and Accurate Rotation Curves (SPARC) sample together with estimates of the large-scale external gravitational field from an all-sky galaxy catalog. Our detection is threefold: (1) the EFE is individually detected at $8\sigma$ to $11\sigma$ in "golden" galaxies subjected to exceptionally strong external fields, while it is not detected in exceptionally isolated galaxies, (2) the EFE is statistically detected at more than $4\sigma$ from a blind test of 153 SPARC rotating galaxies, giving a mean value of the external field consistent with an independent estimate from the galaxies' environments, and (3) we detect a systematic downward trend in the weak gravity part of the radial acceleration relation at the right acceleration predicted by the EFE of the MOND modified gravity. Tidal effects from neighboring galaxies in the $\Lambda$CDM context are not strong enough to explain these phenomena. They are not predicted by existing $\Lambda$CDM models of galaxy formation and evolution, adding a new small-scale challenge to the $\Lambda$CDM paradigm. Our results point to a breakdown of the SEP, supporting modified gravity theories beyond General Relativity.<br />Comment: ApJ (published), 14 figures, 2 tables (several environmental gravitational fields corrected, Table 2 indexing error fixed, and Figs 5 & 6 revised from an Erratum accepted for publication)
- Subjects :
- High Energy Physics - Theory
Cosmology and Nongalactic Astrophysics (astro-ph.CO)
010504 meteorology & atmospheric sciences
General relativity
Dark matter
FOS: Physical sciences
Context (language use)
General Relativity and Quantum Cosmology (gr-qc)
Astrophysics
Astrophysics::Cosmology and Extragalactic Astrophysics
01 natural sciences
General Relativity and Quantum Cosmology
Gravitation
Gravitational field
0103 physical sciences
Galaxy formation and evolution
010303 astronomy & astrophysics
Galaxy rotation curve
Astrophysics::Galaxy Astrophysics
0105 earth and related environmental sciences
Physics
Astronomy and Astrophysics
Astrophysics - Astrophysics of Galaxies
Galaxy
High Energy Physics - Theory (hep-th)
Space and Planetary Science
Astrophysics of Galaxies (astro-ph.GA)
Physics::Space Physics
Astrophysics - Cosmology and Nongalactic Astrophysics
Subjects
Details
- Language :
- English
- Database :
- OpenAIRE
- Accession number :
- edsair.doi.dedup.....7d1bf16607e7268d2d87d3c441a503a9